Upon successful completion of screening questionnaire, urine drug, and urine pregnancy subjects will be scheduled for an MRI. On the day of the study subjects will receive an intravenous catheter (IV) for study drug and fluids. Set one of MRI scans will be done with no dexmedetomidine. Set two of scans will be done when subject is anesthetized with dexmedetomidine with the goal depth of sedation will be moderate sedation. Set three of scans will be done when dexmedetomidine is stopped and wakefulness is achieved.